Variable displacement swash plate compressor

ABSTRACT

A variable displacement swash plate compressor comprises a rotating shaft, a swash plate fitted on the rotating shaft to engage the rotating shaft slidably and to be variable in inclination relative to the rotating shaft, thereby rotating synchronously with the rotating shaft, a first spring for forcing the swash plate in the direction decreasing the inclination of the swash plate, a second spring for forcing the swash plate inclined to near the minimum inclination in the direction increasing the inclination of the swash plate, and a damper for countering the short period variation of the inclination of the swash plate inclined to near the minimum inclination.

BACKGROUND OF THE INVENTION

The present invention relates to a variable displacement swash platecompressor.

Japanese Patent Laid-Open Publication No. 2000-002180 teaches a variabledisplacement swash plate compressor comprising a rotating shaft, a swashplate fitted on the rotating shaft to engage the rotating shaft slidablyand to be variable in inclination relative to the rotating shaft,thereby rotating synchronously with the rotating shaft, a first springfor forcing the swash plate in the direction decreasing the inclination,and a second spring for forcing the swash plate inclined to near theminimum inclination in the direction increasing the inclination.

When the variable displacement swash plate compressor is operated withthe swash plate inclined to near the minimum inclination, the loadacting on the compressor becomes nearly zero. As a result, the biasingforces of the first spring and the second spring become the primaryforces acting on the swash plate, the inclination of the swash platebecomes liable to increase and decrease repeatedly with a short periodnear the minimum inclination owing to the telescopic motions of the twosprings, and the swash plate becomes liable to move unstably. Theunstable movement of the swash plate causes wear and fatigue of theelements of the compressor.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a variable displacementswash plate compressor comprising a rotating shaft, a swash plate fittedon the rotating shaft to engage the rotating shaft slidably and to bevariable in inclination relative to the rotating shaft, thereby rotatingsynchronously with the rotating shaft, a first spring for forcing theswash plate in the direction decreasing the inclination, and a secondspring for forcing the swash plate inclined to near the minimuminclination in the direction increasing the inclination, wherein shortperiodical increase and decrease of the inclination of the swash plateinclined to near the minimum inclination is prevented.

In accordance with the present invention, there is provided a variabledisplacement swash plate compressor comprising a rotating shaft, a swashplate fitted on the rotating shaft to engage the rotating shaft slidablyand to be variable in inclination relative to the rotating shaft,thereby rotating synchronously with the rotating shaft, a first springfor forcing the swash plate in the direction decreasing the inclinationof the swash plate, a second spring for forcing the swash plate inclinedto near the minimum inclination in the direction increasing theinclination of the swash plate, and a damper for countering the shortperiod variation of the inclination of the swash plate inclined to nearthe minimum inclination.

In the variable displacement swash plate compressor of the presentinvention, the damper counters the short period variation of theinclination of the swash plate inclined to near the minimum inclinationto prevent the short periodical increase and decrease of the inclinationof the swash plate inclined to near the minimum inclination.

In a preferred embodiment of the present invention, the damper forms acase for accommodating the second spring.

When the damper forms a case for accommodating the second spring, thecompressor becomes smaller than that wherein the damper is disposedindependent of the second spring.

In another preferred embodiment of the present invention, the secondspring fits on the rotating shaft, the damper comprises a cylindricalbody provided with an annular bottom wall opposing the swash plate andslidably fitting on the rotating shaft and a circumferential sidewall,and a cap slidably fitting in the open end of the cylindrical body andfitting on the rotating shaft, the second spring abuts the bottom wallof the cylindrical body at the end adjacent to the swash plate and abutsthe cap at the end distanced from the swash plate, and the cap isprevented from moving in the direction away from the swash plate.

When the second spring fits on the rotating shaft, the damper providedwith the aforementioned simple structure can prevent the shortperiodical increase and decrease of the inclination of the swash plateinclined to near the minimum inclination.

In another preferred embodiment of the present invention, a snap ringfixed to the rotating shaft prevents the cap from moving in thedirection away from the swash plate.

In another preferred embodiment of the present invention, the cap ispress fitted on the rotating shaft to be prevented from moving in thedirection away from the swash plate.

The cap can be prevented from moving in the direction away from theswash plate by snap ring fixed to the rotating shaft or by press fittingon the rotating shaft.

In another preferred embodiment of the present invention, thecylindrical body or the cap is provided with a pore.

The damping force of the damper against the short periodical increaseand decrease of the inclination of the swash plate can be adjusted byadjusting the size of the pore formed in the cylindrical body or thecap.

In another preferred embodiment of the present invention, thecircumferential sidewall of the cylindrical body is provided with a poreelongated in the longitudinal direction of the cylindrical body, theelongated pore can overlap the cap, and the opening area of theelongated pore decreases as the inclination of the swash platedecreases.

When the inclination of the swash plate becomes minimum, the openingarea of the elongated pore becomes minimum to maximize the damping forceagainst the short periodical increase and decrease of the inclination ofthe swash plate, thereby effectively preventing the short periodicalincrease and decrease of the inclination of the swash plate inclined tonear the minimum inclination.

In another preferred embodiment of the present invention, thecylindrical body is provided with a projection for abutting the end faceof the cap distanced from the bottom wall of the cylindrical body at theopen end.

The projection prevents the cylindrical body from leaving the cap.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a sectional view of a variable displacement swash platecompressor in accordance with the first preferred embodiment of thepresent invention.

FIG. 2 is an enlarged sectional view of the damper of the variabledisplacement swash plate compressor in accordance with the firstpreferred embodiment of the present invention.

FIG. 3 is an enlarged sectional view of the damper of a variabledisplacement swash plate compressor in accordance with the secondpreferred embodiment of the present invention.

FIG. 4 is a set of structural views of the damper of a variabledisplacement swash plate compressor in accordance with the thirdpreferred embodiment of the present invention. FIGS. 4(a) and 4(c) areenlarged sectional views, and FIGS. 4(b) and 4(d) are perspective views.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A variable displacement swash plate compressor in accordance with thefirst preferred embodiment of the present invention will be described.

As shown in FIG. 1, a variable displacement swash plate compressor A isprovided with a rotating shaft 10, a rotor 11 fixed to the rotatingshaft 10, and a swash plate 12 fitted on the rotating shaft 10 to engagethe rotating shaft 10 slidably and to be variable in inclinationrelative to the rotating shaft 10. The swash plate 12 is connected tothe rotor 11 through a linkage 13 to be variable in inclination relativeto the driving shaft 10, thereby rotating synchronously with therotating shaft 10.

A first spring 14 is disposed between the rotor 11 and the swash plate12 and fits on the rotating shaft 10 to force the swash plate 12 in thedirection decreasing the inclination of the swash plate 12. A secondspring 15 fits on the rotating shaft 10 to force the swash plate 12 inthe direction increasing the inclination of the swash plate 12. Thefirst spring 14 and the second spring 15 are disposed to face oppositesurfaces of the swash plate 12.

A plurality of pistons 17 engage the swash plate 12 through a pluralityof pairs of shoes 16 that slidably engage the outer peripheral portionof the swash plate 12. The pistons 17 are inserted into cylinder bores18 a formed in a cylinder block 18.

The plurality of pairs of shoes 16, the pistons 17 and the cylinderbores 18 a are distanced from each other in the circumferentialdirection.

The rotor 11, the swash plate 12, the linkage 13, the shoes 16 and thepistons 17 form a compressing mechanism driven by the rotating shaft 10.

A cylindrical front housing 20 provided with a bottom wall forms a crankchamber 19 for accommodating the rotating shaft 10, the rotor 11 and theswash plate 12. The fore end portion of the rotating shaft 10 passesthrough the bottom wall of the front housing 20 to extend out of thefront housing 20.

A seal member 21 is disposed in the annular space between the bottomwall of the front housing 20 and the rotating shaft 10.

A rotating force is transferred from a power source not shown in thefigures to the fore end portion of the rotating shaft 10.

A cylinder head 22 is installed to form an inlet chamber 22 a and anoutlet chamber 22 b.

A valve plate 23 is disposed between the cylinder block 18 and thecylinder head 22. The valve plate 23 is provided with inlet holes 23 aand outlet holes 23 b communicating with the cylinder bores 18 a. Inletvalves 24 and outlet valves 25 are fitted to the valve plate 23.

The front housing 20, the cylinder block 18, the valve plate 23 and thecylinder head 22 are assembled as a unitary body by a plurality ofthrough bolts 26 circumferentially distanced from each other.

The rotating shaft 10 is rotatably supported by radial bearings 27 and28 disposed in the front housing 20 and the cylinder block 18. The rotor11 is rotatably supported by a thrust bearing 29 disposed in the fronthousing 20.

A damper 30 is disposed to accommodate the second spring 15.

As shown in FIG. 2, the damper 30 comprises a cylindrical body 31provided with an annular bottom wall 31 a opposing the swash plate 12and slidably fitting on the rotating shaft 10 and a circumferentialsidewall 31 b, and a cap 32 slidably fitting in the cylindrical body 31and slidably fitting on the rotating shaft 10. The second spring 15abuts the bottom wall 31 a of the cylindrical body 31 at the endadjacent to the swash plate 12 and abuts the cap 32 at the end distancedfrom the swash plate 12. The cap 32 is restricted from moving in thedirection away from the swash plate 12 by a snap ring 33 fixed to therotating shaft 10.

The cylindrical body 31 is provided with projections 31 c at the openend. The projections 31 c can abut the end face of the cap 32 distancedfrom the bottom wall 31 a of the cylindrical body 31.

The operation of the variable displacement swash plate compressor A isas follows.

Rotating force is transferred to the rotating shaft 10 from the externalpower source not shown in the figures, and rotation of the rotatingshaft 10 is transferred to the swash plate 12 through the rotor 11 andthe linkage 13. The rotation of the swash plate 12 causes reciprocalmovement of the peripheral portion of the swash plate 12 in thelongitudinal direction of the rotating shaft 10. The reciprocal movementof the peripheral portion of the swash plate 12 is transferred to thepistons 17 through the shoes 16, and the pistons 17 move reciprocally inthe cylinder bores 18 a. Refrigerant gas enters into the inlet chamber22 a from an external refrigerant circuit through an inlet port formedin the cylinder head 22. The refrigerant gas is sucked into the cylinderbores 18 a through the inlet holes 23 a and the inlet valves 24 to bepressurized in the cylinder bores 18 a. The pressurized refrigerant gasin the cylinder bores 18 a discharges into the outlet chamber 22 bthrough the outlet holes 23 b and the outlet valves 25, and thendischarges from the outlet chamber 22 b into the external refrigerantcircuit through an outlet port formed in the cylinder head 22.

A displacement control valve not shown in the figures controls theintroduction of the pressurized refrigerant gas in the outlet chamber 22b into the crank chamber 19 to control the internal pressure in thecrank chamber 19 and the inclination of the swash plate 12, therebycontrolling displacement of the variable displacement compressor A.

When the inclination of the swash plate 12 decreases, the first spring14 extends to force the swash plate 12 toward the cylinder block 18. Theswash plate 12 moves toward the cylinder block 18 and the inclination ofthe swash plate 12 decreases. When the inclination of the swash plate 12decreases to a predetermined angle near the minimum inclination angle,the swash plate 12 abuts the bottom wall 31 a of the damper 30. When theinclination of the swash plate 12 further decreases, the swash plate 12further moves toward the cylinder block 18 and forces the cylindricalbody 31 toward the cap 32. The cylindrical body 31 slides toward the cap32 and contracts the second spring 15 that abuts the cap 32 preventedfrom moving in the direction away from the swash plate 12 by the snapring 33 and is prevented from rigid body movement.

When the inclination of the swash plate 12 increases, the second spring15 extends to force the swash plate 12 toward the front housing 20. Theprojections 31 c prevent the cylindrical body 31 from leaving the cap32.

When the variable displacement swash plate compressor A is operated withthe swash plate 12 inclined to near the minimum inclination, the loadacting on the compressor A becomes nearly zero. As a result, the biasingforces of the first spring 14 and the second spring 15 become theprimary forces acting on the swash plate 12. Therefore, generallyspeaking, the inclination of the swash plate 12 becomes liable toincrease and decrease repeatedly with a short period near the minimuminclination owing to the telescopic motions of the springs 14 and 15,and the swash plate 12 becomes liable to move unstably. The unstablemovement of the swash plate 12 causes wear and fatigue of the elementsof the compressor A.

However, in the variable displacement swash plate compressor A, theswash plate 12 abuts the bottom wall 31 a of the damper 30 when theinclination of the swash plate decreases to near the minimuminclination. When the inclination of the swash plate 12 repeats theincrease and decrease near the minimum inclination, and the swash plate12 repeats reciprocally the movement toward the cylinder block 18 andthe movement toward the front housing 20, while abutting the bottom wall31 a of the damper 30, the cylindrical body 31 repeats reciprocally themovement toward the cap 32 and the movement away from the cap 32 underthe biasing force of the second spring 15. The space enclosed by therotating shaft 10, the cylindrical body 31 and the cap 32 is filled withthe refrigerant gas and lubrication oil. When the cylindrical body 31repeats reciprocally the movement toward the cap 32 and the movementaway from the cap 32, discharging of the refrigerant gas and thelubrication oil from the aforementioned space and sucking of therefrigerant gas and the lubrication oil into the aforementioned spaceare repeated reciprocally through the clearances formed in the slidableabutments between the rotating shaft 10 and the bottom wall 31 a of thecylindrical body 31, the rotating shaft 10 and the cap 32, and the cap32 and the circumferential wall 31 b of the cylindrical body 31. Whenthe refrigerant gas and the lubrication oil are discharged from andsucked into the aforementioned space through the aforementionedclearances formed in the slidable abutments, resistance forceproportional to the flow velocity of the refrigerant gas and thelubrication oil is generated due to the viscosities of the refrigerantgas and the lubrication oil. The resistance force prevents the shortperiod discharging of the refrigerant gas and the lubrication oil fromthe aforementioned space and the short period sucking of the refrigerantgas and the lubrication oil into the aforementioned space, the shortperiod reciprocal movement of the cylindrical body 31 and the swashplate 12, the short period increase and decrease of the inclination ofthe swash plate 12, and the unstable movement of the swash plate 12.

The damper 30 forms a case for accommodating the second spring 15.Therefore, the compressor A becomes smaller than that wherein the damper30 is disposed independent of the second spring 15.

When the second spring 15 fits on the rotating shaft 10, the damper 30can be provided with the aforementioned simple structure to prevent theshort period increase and decrease of the inclination of the swash plate12 inclined to near the minimum inclination.

As shown in FIG. 3, the cap 32 can be press fitted on the rotating shaft10. The cap 32 is prevented from moving in the direction away from theswash plate 12. Thus, the snap spring 33 can be removed and the numberof elements decreases.

The bottom wall 31 a of the cylindrical body 31 can be provided withsmall pores 31 d as shown in FIGS. 4(a) and 4(b). The circumferentialsidewall 31 b of the cylindrical body 31 can be provided with smallpores 31 e as shown in FIGS. 4(c) and 4(d).

The resistance force against the flow of the refrigerant gas and thelubricating oil through the small pores 31 d and 31 e can be adjustedand the damping force of the damper 30 against the short period increaseand decrease of the inclination of the swash plate 12 inclined to nearthe minimum inclination can be adjusted by adjusting the opening areasof the small pores 31 d and 31 e.

The small pores 31 e can be elongated in the longitudinal direction ofthe cylindrical body 31 to form elongated pores 31 e′ as shown in FIG.4(c). The elongated pores 31 e′ can overlap the cap 32 and the openingareas thereof decrease as the inclination of the swash plate decreases.When the inclination of the swash plate 12 becomes minimum, the openingareas of the elongated pores 31 e′ become minimum to maximize thedamping force against the short period increase and decrease of theinclination of the swash plate 12, thereby effectively preventing theshort period increase and decrease of the inclination of the swash plate12 inclined to near the minimum inclination.

The cap 32 can be provided with small pores 31 f as shown in FIGS. 4(a).The resistance force against the flow of the refrigerant gas and thelubricating oil through the small pores 31 f can be adjusted and thedamping force of the damper 30 against the short period increase anddecrease of the inclination of the swash plate 12 inclined to near theminimum inclination can be adjusted by adjusting the opening area of thepore small pores 31 f.

While the present invention has been described with reference topreferred embodiments, one of ordinary skill in the art will recognizethat modifications and improvements may be made while remaining withinthe spirit and scope of the present invention. The scope of theinvention is determined solely by the attached claims.

1. A variable displacement swash plate compressor comprising a rotatingshaft, a swash plate fitted on the rotating shaft to engage the rotatingshaft slidably and to be variable in inclination relative to therotating shaft, thereby rotating synchronously with the rotating shaft,a first spring for forcing the swash plate in the direction decreasingthe inclination of the swash plate, a second spring for forcing theswash plate inclined to near the minimum inclination in the directionincreasing the inclination of the swash plate, and a damper forcountering the short period variation of the inclination of the swashplate inclined to near the minimum inclination.
 2. A variabledisplacement swash plate compressor of claim 1, wherein the damper formsa case for accommodating the second spring.
 3. A variable displacementswash plate compressor of claim 2, wherein the second spring fits on therotating shaft, the damper comprises a cylindrical body provided with anannular bottom wall opposing the swash plate and slidably fitting on therotating shaft and a circumferential sidewall, and a cap slidablyfitting in the open end of the cylindrical body and fitting on therotating shaft, the second spring abuts the bottom wall of thecylindrical body at the end adjacent to the swash plate and abuts thecap at the end distanced from the swash plate, and the cap is preventedfrom moving in the direction away from the swash plate.
 4. A variabledisplacement swash plate compressor of claim 3, wherein a snap ringfixed to the rotating shaft prevents the cap from moving in thedirection away from the swash plate.
 5. A variable displacement swashplate compressor of claim 3, wherein the cap is press fitted on therotating shaft to be prevented from moving in the direction away fromthe swash plate.
 6. A variable displacement swash plate compressor ofclaim 3, wherein the cylindrical body or the cap is provided with a poreformed therethrough.
 7. A variable displacement swash plate compressorof claim 3, wherein the circumferential sidewall of the cylindrical bodyis provided with a pore formed therethrough and elongated in thelongitudinal direction of the cylindrical body, and wherein theelongated pore overlaps the cap and the opening area of the elongatedpore decreases as the inclination of the swash plate decreases.
 8. Avariable displacement swash plate compressor of claim 3, wherein thecylindrical body is provided with a projection for abutting the end faceof the cap distanced from the bottom wall of the cylindrical body at theopen end.
 9. A variable displacement swash plate compressor of claim 4,wherein the cylindrical body or the cap is provided with a pore formedtherethrough.
 10. A variable displacement swash plate compressor ofclaim 5, wherein the cylindrical body or the cap is provided with a poreformed therethrough.
 11. A variable displacement swash plate compressorof claim 4, wherein the circumferential sidewall of the cylindrical bodyis provided with a pore formed therethrough and elongated in thelongitudinal direction of the cylindrical body, and wherein theelongated pore overlaps the cap and the opening area of the elongatedpore decreases as the inclination of the swash plate decreases.
 12. Avariable displacement swash plate compressor of claim 5, wherein thecircumferential sidewall of the cylindrical body is provided with a poreformed therethrough and elongated in the longitudinal direction of thecylindrical body, and wherein the elongated pore overlaps the cap andthe opening area of the elongated pore decreases as the inclination ofthe swash plate decreases.
 13. A variable displacement swash platecompressor of claim 4, wherein the cylindrical body is provided with aprojection for abutting the end face of the cap distanced from thebottom wall of the cylindrical body at the open end.
 14. A variabledisplacement swash plate compressor of claim 5, wherein the cylindricalbody is provided with a projection for abutting the end face of the capdistanced from the bottom wall of the cylindrical body at the open end.15. A variable displacement swash plate compressor of claim 6, whereinthe cylindrical body is provided with a projection for abutting the endface of the cap distanced from the bottom wall of the cylindrical bodyat the open end.
 16. A variable displacement swash plate compressor ofclaim 7, wherein the cylindrical body is provided with a projection forabutting the end face of the cap distanced from the bottom wall of thecylindrical body at the open end.
 17. A variable displacement swashplate compressor of claim 9, wherein the cylindrical body is providedwith a projection for abutting the end face of the cap distanced fromthe bottom wall of the cylindrical body at the open end.
 18. A variabledisplacement swash plate compressor of claim 10, wherein the cylindricalbody is provided with a projection for abutting the end face of the capdistanced from the bottom wall of the cylindrical body at the open end.19. A variable displacement swash plate compressor of claim 11, whereinthe cylindrical body is provided with a projection for abutting the endface of the cap distanced from the bottom wall of the cylindrical bodyat the open end.
 20. A variable displacement swash plate compressor ofclaim 12, wherein the cylindrical body is provided with a projection forabutting the end face of the cap distanced from the bottom wall of thecylindrical body at the open end.